Expander



19-42- F. w. WlLKENlh IG 2,293,450

EXPANDER Filed Dec. 7, 1940 4 Sheets-Sheet l F. w. WIVLKENING EXPANDER Aug. '1 8, 1942.

Filed Dec. '7, 1940 4 Sheets-Sheet 2 61M W S ZC-ZZZ ATTORNEY.

. Aug. 18, 1942.

F. w. WILKENING 2,293,450

EXPANDER Filed Dec. 7, 1940 4 Sheets-Sheet 3 INVENTOR.

Z fft rc'e BEL/755%? Aug. 18, 1942.

E. w. WIL KEN|NG EXPANDER Filed Dec. 7, 1940 4 Sheets-Sheet 4 7 /Off ATTORNEY.

Patented Aug. 18, 1942 EXPANDER Frederick W. Wilkening, Narberth, Pa., assignor to Wilkening Manufacturing Company, Philadelphia, Pa., a corporation of Delaware Application December 7, 1940, Serial No. 368,990

1 Claim.

The present invention, relates to certain new and useful expanders and more particularly to self-expanding expanders for piston rings.

An object of the present invention is to provide an expander for piston rings which will be more efficient and will follow the piston ring more closely than present type expanders, and which will provide a more uniform and continuous support, at the same time simplifying the piston ring construction.

Other objects and purposes will be apparent from the following specification and appended claim, and the accompanying drawings.

For the purpose of illustrating the invention, there are shown in the accompanying drawings forms thereof which are at present preferred, since the same have been found in practice to give satisfactory and reliable results, although it is to be understood that the various instrumentalities of which the invention consists can be variously arranged and organized and that the invention is not limited to the precise arrangement and organization of the instrumentalities as herein shown and described.

Referring to the accompanying drawings, in which like reference characters indicate like parts,

Figure 1 represents a perspective View of one embodiment of the expander constituting the present invention, as it appears in actual use with a piston ring;

Figure 2 represents a fragmentary perspective View, on a much enlarged scale, of the expander and the piston ring shown in Figure l, as they would appear when assembled in a piston and cylinder; parts being broken away, more clearly to show the construction thereof;

Figure? represents a perspective view of one embodiment of the expander constituting the present invention, in which the strip of which said expander is formed is circular in cross-section and in which one method of joining the free end of said strip, namely by spot-welding, is shown;

Figure 4 represents a fragmentary perspective view of the expander shown in Figure 3, but in which an alternative means of fastening the free ends thereof is usednamely, a collar or clip into which said free ends are inserted;

Figure 5 represents a fragmentary perspective View similar to that of Figure 4, of another embodiment of the present expander constructed of a strip having a square cross-section;

Figure 6 represents a fragmentary perspective view of another embodiment of the expander constituting, the present invention in which a strip having a rectangular cross-section has been used and in which the corrugations are more shallow than those shown in Figure 5';

Figure 7 represents a fragmentary perspective view of still another embodiment of the present invention, in which a strip having a. round cross-section has been used and in which a different type of flattened, or acute-angled corrugation has been used;

Figure 8 represents a fragmentary perspective View similar to that of Figure 7 and showing the same type of corrugations as shown in Figure 7, but in which a strip having a square cross-section has been used;

Figure 9 represents a perspective view of one embodiment of the expander constituting the present invention as it would appear when used with a three-piece, oil-control, piston ring, the expander shown being that illustrated in Figure 5; the parts being disassembled better to show the construction thereof;

Figure 10 represents a perspective view similar to that of Figure 9, showing the expander illustrated in Figure 8 as used with a three-piece, oilcontrol piston ring having a different type of intermediate spacing member than that shown in Figure 9; the parts being disassembled better to show the construction thereof;

Figure. 11 represents, a fragmentary perspective view showing an intermediate stage in the formation of the expander shown in Fi ures 3 and ll-namely the stage in which the corrugations have already been formed but before the corrugated strip has been formed into its, final circular shape with its free ends fastened together;

Figure 12 represents a fragmentary perspective view similar to that of Figure 11 but showing the expander illustrated in Figure 7;

Figure 13 represents a fragmentary perspective View similar to that of Figure 11, but showing the expander illustrated in Figure 8;

Figure 14 represents a, fragmentary perspective view similar to that of Figure 11, but showing the expander illustrated in Figure 6;

Figure 15 represents a fragmentary perspective View similar to that of Figure 11, but showing the expander illustrated in Figure 5;

Figure 16 represents a composite View, partly in section and partly in elevation, of a piston as it appears assembled in a cylinder, and being equipped, for purposes of illustration, with different embodiments of the expander constituting the present invention, and with different types of compression and oil-control piston rings;

Figure 1'7 represents a fragmentary perspective view similar to that of Figure 2, but showing the expander and piston ring illustrated in Figure 9;

Figure 18 represents a fragmentary perspective View similar to that of Figure 2, but showing the expander and piston ring illustrated in Figure Figure 19 represents a fragmentary perspective View similar to that of Figure 2, but showing the expander and piston ring illustrated in the top groove of the piston shown in Figure Figure 20 represents a perspective view of an expander similar to that shown in Figure 19, but formed of a strip having a round cross-section; and

Figure 21 represents a horizontal, cross-sectional View along the line 2 l2l of Figure 16.

In one embodiment of the present invention, as shown in Figures 1 to 5 inclusive, and Figure 11, a length of tempered steel spring wire 29 is corrugated to form a series of alternating loops 22 and 22 and nodes 23 arranged in a generally vertical plane as indicated in Figur 11. The wire 20 has preferably a diameter of more or less approximately .O2O inch, although this diameter may vary from .015 to .030 inch or, in certain cases, through even wider limits.

This corrugation may be produced by means of corrugating rolls or bending pins or by a corrugating press.

Instead of the wire 29, a wire 2! which is square in cross-section may be used as shown in Figures 5, 9 and 17, or a Wire 2la which is rectangular in cross-section may be used, as shown in Figures 6 and 19. It is also possible to use wire of different cross-section, such as, for example, polygonal, With parallel or non-parallel sides, or noncircular, such as oval or other curved cross-section.

It is preferred to corrugate a wire of considerable length and to subsequently cut off strips, as shown in Figures 11 to 15 inclusive, of the corrugated wire of appropriate length depending upon the size of the piston ring to be supported thereby. This length is slightly longer than the inside circumference of the piston ring to be supported, so that in the final assembled piston ring the expander will be slightly compressed by the piston ring. It is possible, however, first to cut the uncorrugated wire into appropriate lengths and then subsequently to corrugate the individual pieces separately (for example, in a corrugating press it is possible to corrugate a large number of individual strips at one time); the lengths of the uncorrugated strips being sufficiently larger than the length of corrugated wire desired to allow for the corrugations to be formed.

After the corrugated strip of wire has been formed, it is then shaped into an annulus or ring 25 in which the loops 22 and 22 extend in a generally axial plane.

This annulus 25 is formed either by generally shaping the corrugated strip giving each portion thereof a generally circular curvature'or by merely taking the two ends 23 and 21 of the strip and bringing them into abutment with each other.

The ends 25 and 2'! are then fastened to each other by butt-welding or spot-welding or other welding or brazing as shown in Figure 3, or by intertwining the ends 26 and 21 or by slipping said ends 26 and 21 into a small tube or clip 28 as shown in Figure 4, whereupon the tension of the ring 25 will tend to hold said ends 26 and 27 firmly in the tube 23; it is possible, however, to

crimp the ends 29 and 39 of the tube 28 in order to aid in maintaining a firm contact until the expander is installed in the piston.

It is also possible to form more shallow corrugations, that is, corrugations in which the amplitude (the vertical distance from a loop to a node) is less than that shown in Figures 1 to 5 inclusive.

Thus, Figures 6 and 19 show an expander having such shallow corrugations, the expander being formed of a strip which is rectangular in cross-section; it is, however, possible to make an expander having such shallow corrugations equally Well out of a strip having round or square or other cross-section.

As shown in Figures 7, 8, 10, 18 and 20, the expander of the present invention can be formed with non-sinuous, or flattened, or angled corrugations. While the embodiment shown consists of a series of acute-angled bends, it is possible to form the corrugations with right-angled bends or with obtuse-angled bends, or with combinations of dififerent angled bends.

The expander of the present invention is preferably formed of strip steel or ribbon steel, previously tempered to a desired degree of hardness and resilience, no subsequent tempering or annealing or other treatment being required after the corrugating operation. The expander of the present invention, when installed in a piston with a piston ring, as will be hereinafter described, is an annulus having a high degree of resilience, so that it urges the piston ring radially outwardly with a circumferentially uniform force, thereby maintaining the cylinder-contacting portion of said piston ring in firm contact with the cylinder Wall.

The expander of the present invention can be used equally Well with compression rings and with oil-control rings. It is equally efiicient on onepiece rings or on multi-piece rings; such as for example, oil-control rings having upper and lower cylinder-contacting elements and an axially-intermediate spacing element.

Thus, in Figure 16 is shown a piston 3| provided with annular grooves 32, 33, 34 and 35 and having annularly distributed, radially-extending passageways 36, extending through the wall 3! of said piston 3i and communicating with the three lower grooves 33, as and 35.

For purposes of illustration, Figure 16 shows a compression ring 38 installed in the uppermost groove 32 of the piston 3|. Along the radially inner periphery of the ring 33 is formed the annular groove 53 which is produced by radiallyinwardly-protruding, upper and lower, annular shoulder 59 and 69. Continuously contacting this ring 38 and forcing it radially outwardly is the expander 25c. This expander 25-c is rectangular in cross-section and has a relatively smaller amplitude 6! (that is, the corrugations are shallower) than the amplitude of expanders 25--a, 25-b or 25d. The expander 25c fits within the annular groove 58 of the piston ring 38. The groove 58 thus serves to anchor the expander 25c and also eliminates contact of said expander 25c with the upper and lower walls of the groove 32. It is also possible to use other types of expanders having shallow corrugations within the groove 58; for example, the expander may be square in cross-section or polygonal or may be circular or non-circular in cross-secion.

A one-piece, oil-control, piston ring .39 is shown in the second groove 33 of the piston. Continuously contacting this ring 39 and forcing it radially outward is the expander iii-a. The ring 39 is provided with upper and lower Walls 52 and 53 forming upper and lower cylinder-contacting surfaces 54 and 55 respectively, and an integrally formed, central annulus 55 in which are provided circumferentially-distributed openings 51 communicating with the openings 36 in the piston wall 3! and providing for passage of oil therethrough. The expander 25a is the embodiment shown in Figures 1 to 5 inclusive and is composed of a cross-sectionally circular strip forming an annulus in which the corrugations. are relatively deeper than those of expander 25c, so that the expander extends axially for the same distance as the ring 39, thus supporting the entire back surface of said ring 39. While the ring shown in this instance is circular in cross-section, itis possible to support this one-piece oil-control piston ring 39 with other embodiments of the expander constituting the present invention; that is, the expander could be formed of a strip which is non-circular or square or rectangular or polygonal in cross-section. Similarly, the expander used with ring 39 could be non-sinuous or flattened or angled as shown in Figures 7 and 8.

Inserted in groove 34 is shown an oil-control ring 4|] of the type indicated in Figures 9 and 17, which consists of separate upper and lower, split, cylinder-contacting rings 4| and 42, respectively, and an intervening, split, spacer ring 43 which is composed of a thin central annulus 44 and circumferentially distributed spacer members 45 which extend axially above and below said annulus 44 and provide shoulders 45 and 4! which make contact with said rings 4| and 42 respectively. The rings 4| and 42 and the spacer 43 are preferably formed of steel, although they may be made of cast iron or other suitable material. The rings 4| and 42 and the spacer 43 all have the same inside diameter while the outside diameter of the rings 4| and 42 is identical but is greater than the outside diameter of the spacer 43. As a result, the expander 25-17, which has a relatively square cross-section as shown in Figures 8, 9, 13 and 17, contacts the inner periphery of all three rings, namely the cylinder-contacting rings 4| and 42 and the spacer ring 43. Alternate loops 22 and 22' of the expander 25b will contact and support and urge radially outwardly the upper 4| and lower 42 cylinder-contacting rings, respectively. The nodes or intermediate portions 23 of the expander 25b will contact and support and urge radially outwardly the spacer ring 43. However, due to the smaller outside diameter of said spacer ring 43, only the rings 4| and 42 make contact with the wall 43 of the cylinder 49, the outer periphery of said spacer ring 43 falling short of said wall 48 and being recessed within said rings 4| and 42. The space 5! between the rings 4| and 42 and the spacer 43 permits the passage of oil therethrough and through the communicating openings 35 in the wall 3'! of the piston 3|.

The lowermost groove 35 is shown provided with a three-piece, oil-control piston ring 5| composed of split, upper and lower, cylindercontacting rings 4| and 42 respectively, and the intervening split, spacer member 43a having upper and lower thin, fiat annuli 44a and 44'-b and intervening axial extensions 45a, which are circumferentially distributed between said annuli 44a and 44b and so that they serve as axial supports and spacers for the annuli 44-a and 44-b, the upper surface of annulus 44a contacting and supporting ring 4| while the lower surface of the annulus 44b similarly contacts and supports ring 42. Continuously contacting said ring 5| and urging it radially outwardly with a circumferentially uniform force is the expander 25-d. This expander is of the non-sinuous or flattened or angled type shown in Figures 5, 10 and 18, and consists of alternate flattened loops 22--a and 22b, which support and urge radially outwardly the rings 4| and 42, respectively, and the nodes 23-a which support the spacer ring 43--a. Similarly to the oil-control ring 48, in the present ring 5| the upper and lower cylinder-contacting elements 4| and 42 and the intervening spacer member 43-a all have the same inside diameter. The outside diameter of rings 4| and 42 is the same, but is greater than the outside diameter of the intervening spacer member 43-a. As a result, the expander 25-d contacts and supports all three members 4|, 42 and 43a along the inner periphery thereof, while the outer peripheries of rings 4| and 42 only contact the cylinder wall; the outer periphery of the spacer ring 43a falling short of the cylinder-wall and being recessed within the upper and lower cylinder-contacting rings 4| and 42.

While expanders 25-1) and 25-d, as used with rings 43 and 5|, respectively, are shown as having a square cross-section, it is understood and intended that other types of expanders having rectangular or circular or non-circular crosssection may be used as well; if, however, an expander having a curved cross-section (circula'r or non-circular) is used with three-piece oilcontrol rings, such as the type shown in 40 and 5|, it is preferred to have the upper and lower edges of the inner periphery of the several cylinder-contacting and spacing rings made with angled or sharp edges rather than with rounded or curved edges, as is the usual practice, in order to obtain a larger area of contact between the expander and the piston ring element (since, if both were curved, the point of contact would be reduced to a minimum).

While different combinations of expanders 25Ct, 25-4), Z5c and 25d are shown with piston rings of different types (including compression rings, one-piece oil-control rings, and three-piece oil-control rings) in Figure 16, the combinations shown are for purposes of illustration only; it being understood and intended that the different embodiments of the expander constituting the present invention, which are shown in Figure 16 and in the other drawings, can be used interchangeably with different types of compression and oil-control piston rings.

It is preferred to construct the expander constituting the present invention of a high grade of tempered steel, although other metals, including brass, bronze and other alloys may be used, or any other material having the suitable physical properties therefor.

The expander is preferably formed into its closed loop formation (by welding, as shown in Figures 3 and 7, or by fastening with the clip 28, as shown in Figures 4, 5 and 20) previous to its insertion in the groove, 33 of the piston. The closed ring is then expanded somewhat to permit it to clear the outer periphery of the piston so that it can be moved down to the proper groove, whereupon it is permitted to contract into said groove; it is possible, however, to weld or otherwise fasten the expander into its final closed ring formation after it has been placed in the groove. After the expander has been positioned in the groove as described above, the piston ring (either compression ring or oil-control ring and either one-piece oil-control ring or several-piece oil-control ring) is similarly expanded somewhat to clear the outer periphery of the piston and moved down to the proper groove and allowed to contract into said groove as far as permitted by said expander. As stated previously, the expander has a slightly greater outer circumference than the inner circumference of the piston ring, so that the piston ring will tend to contract the expander slightly resulting in a radially outward tension by said expander exerted. uniformly around the circumference of said piston ring. Thus, it can be seen that the expander presses the cylinder contacting elements of the piston ring firmly against the cylinder wall by virtue of its inherent resilience and is itself centered against the inner periphery of said piston ring tending to move away from the axis of the piston. In this way, the expander is entirely independent of th back wall of the groove in the piston resulting in a freefioating support for the piston ring with no radial support from the piston itself. In other words, the expander is of the non-bottoming type making no contact with the back wall of said groove in the piston.

In old-type expanders, the annulus is given shallow, radially extending corrugations, so that the expander contacts alternately the back wall of the groove of the piston, and the radially inner wall of the piston ring. The expander derives its radially outward tension due to the fact that the corrugations are flattened somewhat when the piston and ring are finally assembled in the cylinder. It can be seen that, in this type of structure, the piston ring is supported at comparatively few points, namely at the half a dozen or so points of contact of said expander with the radially inner wall of the piston ring. Thus, at these points of contact, a relatively higher radially outward pressure is exerted upon the piston ring, whereas in the portions of the piston ring intervening the points of contact with the expander, the radially outward pressure exerted upon the piston ring is relatively lower. This uneven pressure is undesirable in a piston ring and causes excessive wear at certain points in the cylinder wall. While this unevenness is not so pronounced where the piston ring is made of relatively stifi material, it is often desirable to make the piston ring of relatively less stiff or relatively more springy material to permit the ring to be capable of s ight radially inward and outward variations from its true circular periphery, so that the piston ring will be capable of expanding or contracting slightly to conform to irregularities in the cylinder wall. It can be seen that, when the piston ring is made of such relatively more resilient material, the variations in radially outward pressure exerted by an expander due to the fact that the piston ring is supported at relatively few points, are greatly exaggerated and result in excessive friction between the ring and the cylinder wall directly opposite the point of contact between the expander and the piston ring producing excessive wear at such points and subsequent loss in power and increase in oil consumption. Thus, in the past, it has been diificult to adapt such flexible piston rings, which are otherwise highly desirable, due to the uneven wear produced by the old-type expanders.

Furthermore, due to the fact that o d-type expanders must rest against the back wall of the groove in the piston, the radial thickness of the ring has had to be carefully proportioned to groove depth. Considerable difficulty also arose in the variations of pressure resulting from different sized piston rings (ranging from normal to somewhat oversized) these problems arising when a cylinder is re-bored to produce a slightly larger diameter.

The expander of the present invention, on the other hand, is an annulus of spring material which is relatively thin and axially corrugated. It presents a continuous line of contact with the radially inner wall of the piston ring and therefore provides a uniform, supporting, radially-outward pressure. It is thus especially well adapted for use with piston rings of relatively more resilient material, although its uniform pressure is also desirable in piston rings of relatively stiffer material.

Furthermore, the expander of the present invention makes no contact whatsoever with the back wall of the groove of the piston. It derives its radially outward tension by reason of the fact that it is a resilient annulus which is compressed slightly by the piston ring when the piston and ring are assembled in the cylinder, so that its inherent resilience urges the piston ring radially outward. The back wall of the groove of the piston, therefore, does not enter into the picture at all as a support for the piston ring or the expander. The depth of the groove is immaterial and the careful proportioning which was previously necessary in order to prevent variations in pressure between normal and oversiz-ed piston rings is entirely eliminated.

The present expander is especially desirable for use with a three-piece piston ring of the character described herein, since it provides numerous points of support for each of the cylinder-contacting rings and the spacer ring.

The expander of the present invention is far more flexible than the old-type expanders and follows the piston ring much more closely than do the old-type expanders.

The expander of the present invention has been found to result in a flatter oil-control curve; that is, the rate of increase in oil consumption with increasing speed of the motor is less. This is very desirable in improving the efliciency of the motor and in cutting down on oil-consumption which is most marked at high speeds.

Where the term free-floating support is used in the following claim it is intended to mean a method of supporting and urging radially outwardly the piston ring without any radial support from the piston itself. Where the term non-bottoming is used in the following claim it is intended to describe a structure in which the expander makes no contact with the radially inward wall or bottom of the piston groove.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore desired that the present embodiments be considered in all respects as ilustrative and not restrictive, reference being had to the appended claim rather than to the foregoing description to indicate the scope of the invention.

Having thus described the invention, what is hereby claimed as new and desired to be secured by Letters Patent is:

A flexible self-expanding expander for a piston ring comprising a continuously axially-corrugat.

being adapted to exert generally uniform radially outward tension upon said piston ring, and a tube of metal or the like disposed about the abutting ends of said strip and adapted to main- 5 tain said ends in abutting relationship.

FREDERICK W. WILKENING. 

